Desvenlafaxine is the main active metabolite of venlafaxine; it is also known as O-desmethylvenlafaxine or desmethylvenlafaxine; it is a selective serotonin and noradrenaline reuptake inhibitor (SSNRI), represented by the following structural formula:

Desvenlafaxine (DSV), chemical name (±)-1-[2-(dimethylamino)-1-(4-hydroxyphenyl)ethyl]cyclohexanol, as well as its pharmaceutically acceptable salts, were firstly described in U.S. Pat. No. 4,535,186, which is incorporated herein in its entirety by reference.
Desvenlafaxine free base can also be named as desvenlafaxine base, or pure or neutral desvenlafaxine. Desvenlafaxine is administered orally, mainly as the succinate salt, for the treatment of depression and menopause-associated vasomotor disorders. Preferably, it is administered as modified-release preparations.
The dose used is from 50 mg to 400 mg per day, preferably once per day. High doses of 400 mg per day can be associated with adverse effects.
Doses between 100 mg and 200 mg per day are not recommended in patients with moderate to severe hepatic insufficiency.
Some patent documents describe the process for preparing desvenlafaxine and its salts, purification methods thereof and pharmaceutical compositions, but none of them refers to the NSF of desvenlafaxine described in the present invention.
Patent document WO2000032555 (U.S. Pat. No. 6,197,828) of Sepracor describes desvenlafaxine base also known as free, neutral or pure base.
Documents WO2002064543 (U.S. Pat. No. 6,673,838) of Wyeth, and WO2000059851 (U.S. Pat. No. 8,269,040) of Sepracor, refer to the product 0-desmethylvenlafaxine succinate.
Documents US2011082213 of Lek Pharma; WO2010060390 and WO2011006455 of Zenti-Va, describe the preparation of desvenlafaxine and/or salts such as D-glucuronate monohydrate, orotic acid, among others.
Documents WO2009138234 of KRKA Tovarna and U.S. Pat. No. 8,481,596 of Lupin Ltd, describe processes for preparing desvenlafaxine using p-toluenesulfonic acid and benzoic acid.
Document WO2009053840 (US2011046231) of Actavis Group PTC, describes desvenlafaxine salts selected from oxalate, benzoate and lactate salts with addition salts of hydrochloric, sulfuric and toluenesulfonic acid, among others.
Document US20090246284 of Actavis Group describes a co-crystal comprising ortho-desmethylvenlafaxine and succinic acid.
Document US20130028937 of Esteve Laboratories refers to a co-crystal of venlafaxine and celecoxib.
No documents referring to the preparation of new solid forms of desvenlafaxine with hydroxybenzoic acid, for example, 3-hydroxybenzoic acid (3-HB), 3,4-dihydroxybenzoic acid (3,4-DHB) and 3,4,5-trihydroxybenzoic acid (3,4,5-THB), among others, were located in the state of the art.
A great amount of combinations with possible co-formers can be envisaged during the process of obtaining new solid forms, however only some of those combinations generate a stable solid form, as demonstrated in the specification of the present application.